SEOUL, Dec. 13 (Yonhap) -- Candidates from the ruling and main opposition parties entered the final stretch of the presidential race with one side guarding against mud-slinging and the other seeking to increase voter turnout in a bid to win South Korea's top elected office, observers said Thursday.

Such last-minute measures come as the last polls that can be published ahead of election day showed Saenuri Party presidential hopeful Park Geun-hye leading her Democratic United Party (DUP) rival Moon Jae-in by a slim margin.

The 10 surveys taken from Sunday through Wednesday and released by local media outlets Thursday showed Park's approval standing at 0.5-6.8 percentage points higher than Moon's rating, with the average gap hovering at the mid 3 percentage point range.

Park Geun-hye (L), Moon Jae-in (Yonhap file photo)

"Saenuri is fighting to hold onto this lead for the next six days while the DUP wants to achieve an upset victory on the election day," said an election watcher.

Highlighting the need to protect their lead, Saenuri election camp officials including Park all raised their voices against what they claim has been indiscriminate negative campaigning by the DUP, and called for restraint.

The conservative party, in particular, raised issue with the iPad and spy agency employee controversy that became big news on the Internet in the past few days.

The iPad tablet issue emerged when Rep. Jung Cheong-rae, a DUP lawmaker, alleged that Park cheated during the televised debate held on Monday by taking a tablet PC into the session.

Such an act could have given Park access to quiok information and data during the live debate and given her an advantage over other presidential candidates. Under rules set by the National Election Broadcasting Debate Commission, candidates can only take printed material into the debate.

Jung has since apologized after Saenuri countered that Park did not carry an iPad into the studio and moved to take legal action for spreading lies to influence election results.

On the standoff over claims that an employee of the National Intelligence Service (NIS) systematically attacked Moon on the Internet following orders from her superiors, Saenuri called on the DUP to substantiate their claim with evidence and pointed out that the purported safehouse where the "illegal activities" took place was in fact the home of the NIS employee that was purchased by her parents two years ago.

The party set up a special committee to examine the case which it sees as violation of the woman's human rights as well as illegal surveillance. The NIS said it too will take legal action against those that drew the agency into the presidential race.

"They submit no evidence yet claim that the young employee engaged in illegal political activities," said party spokesman Park Sun-kyoo said. He said that if the allegations prove to be false, the opposition and its presidential contender should apologize for spreading false information.

Reflecting this view, Park said in a political rally held Wednesday, that while Moon talks about his disdain for mud-slinging, his party is doing its best to tarnish the image of their rival candidate with lies.

"Instead of resorting to such underhanded tactics, it would be advisable if the DUP and its presidential hopeful released policies and pledges that can help the people," she argued.

Park aides said that while the candidate considers the latest attacks as serious, she has called for the Saenuri Party to refrain from taking steps that can be viewed in the same light by the public.

The party said that while there have been calls to publicize damaging information about Moon, it has opted not to do so because it would distract voters from examining Park and what she can offer for the country's future.

The DUP, on the other hand, said the NIS employee issue is still pending and maintained that the latest revelation is part of a broader plot by the spy agency to influence the outcome of this year's election.

It said the police and the National Election Commission had failed to secure the "crime scene" where the alleged illegal activity took place and warned it will release more incriminating evidence that the spy agency was helping Park.

"Authorities effectively gave the NIS employee time to destroy evidence," said party spokesman Jin Sung-joon.

A party official, who acknowledged that Moon is currently trailing in the polls, said the current situation can be overturned if more people decide to vote next Wednesday.

"Although the polls are predicting a tight race, the overall undercurrent is moving favorably and we should be able to win the race in the end," a party source claimed.

He said that in the past week alone Moon has been able to reduce the gap by 0.5 of a percentage point.

"It is true that the last polls before the election date have never been overturned, but this year it is different because there are more people who want a change in government than those that want to keep Saenuri in power for another five years," said Lee In-young chief of DUP's election office.

He argued there are many voters who do not answer surveys, yet will vote for Moon.

The liberal party said that it is aiming to push for a nationwide campaign to increase voter turnout to 77 percent, with Moon claiming he will perform Korean singer-rapper Psy's famous dance moves in downtown Seoul if that number is reached.

Many pollsters predicted that a low turnout will favor Saenuri because its supporters are more loyal, while higher numbers will indicate more young people, who are more liberal in views, are casting ballots, which usually translates into good news for the DUP.

Reflecting this upbeat mood, Rep. Chung Sye-kyun, a senior advisor at Moon's election camp, said the party is going full throttle with all of its resources being directed towards achieving victory.

Sources said that the DUP is asking supporters to call friends and relatives to persuade them to vote for Moon, and to make full use of social networking services to get people interested in the election.

The party, which had relied on winning over supporters of onetime independent candidate Ahn Cheol-soo also said it has decided to hold talks with Saenuri after the elections, to reduce the number of lawmakers from the current 300.

The party had initially rejected the move made by Ahn, but it has since changed its stance because surveys showed public dislike for lawmakers and that many wanted the number of seats in the National Assembly reduced.